JERRY (SEINFELD): I never get enough sleep. I stay up late at night, cause I'm Night Guy. Night Guy wants to stay up late. 'What about getting up after five hours sleep?', oh that's Morning Guy's problem. That's not my problem, I'm Night Guy. I stay up as late as I want. So you get up in the morning, you're ..... (?), you're exhausted, groggy, oooh I hate that Night Guy! See, Night Guy always screws Morning Guy. There's nothing Morning Guy can do. The only Morning Guy can do is try and oversleep often enough so that Day Guy looses his job and Night Guy has no money to go out anymore.
You can punish and intimidate your future self, as you can see.
What about your past self? If Night Guy can predict what Morning Guy will do, Morning Guy is effectively threatening his past self.
An episode of the Noddy animated series has the following plot.
Noddy needs to go pick up Martha Monkey at the station. But it's such a nice, sunny day that he would prefer to play around outside. He gets an idea to solve this dilemma. He casts a duplication spell on himself and his car and tells the duplicate to go fetch Martha while he goes out to play. Later, Noddy is out having fun when he suddenly spots his duplicate. It turns out that the duplicate also preferred playing outside to doing the errand so he also cast a duplication spell. Then they see another duplicate, and another...
I think this story makes for a nice simple illustration of one of our perennial decision theoretic issues: When making decisions you should take into account that agents identical to yourself will make the same decision in the same situation. A common real-life example of the Noddy problem is when we try to pawn off our dietary problems to our future selves.